U.S. patent application number 10/410578 was filed with the patent office on 2004-02-12 for method and apparatus for processing hard material.
Invention is credited to Altshuler, Gregory B., Belikov, Andre V..
Application Number | 20040030326 10/410578 |
Document ID | / |
Family ID | 29250638 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040030326 |
Kind Code |
A1 |
Altshuler, Gregory B. ; et
al. |
February 12, 2004 |
Method and apparatus for processing hard material
Abstract
A method and apparatus are provided for processing a hard
material, for example a hard biological material such as dental
enamel or bone, with optical radiation. A treatment zone of the
material is selectively cleaned of ablation products and other dirt
to enhance processing efficiency, and a tip through which the
optical radiation is applied to the treatment zone of the hard
material is spaced slightly from the treatment zone during at least
a portion of the time that hydrating fluid is being applied to the
zone and/or while air or another gas is applied to the zone to
clean the surface thereof.
Inventors: |
Altshuler, Gregory B.;
(Wilmington, MA) ; Belikov, Andre V.; (St.
Petersburg, RU) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, PC
FEDERAL RESERVE PLAZA
600 ATLANTIC AVENUE
BOSTON
MA
02210-2211
US
|
Family ID: |
29250638 |
Appl. No.: |
10/410578 |
Filed: |
April 9, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60371097 |
Apr 9, 2002 |
|
|
|
Current U.S.
Class: |
606/10 ;
606/13 |
Current CPC
Class: |
A61B 2018/00005
20130101; A61B 2218/006 20130101; A61C 1/0046 20130101; A61C
17/0217 20130101 |
Class at
Publication: |
606/10 ;
606/13 |
International
Class: |
A61B 018/20 |
Claims
What is claimed is:
1. Apparatus for processing a treatment zone of a hard material
with optical radiation from a suitable source including: a tip
through which the radiation is applied to a surface in a treatment
zone of the material; and a mechanism for cleaning the treatment
zone from dirt, including residual product of ablation.
2. Apparatus as claimed in claim 1 including a mechanism for
applying a gas to said surface to clean the surface, said tip being
slightly spaced from said surface during at least most of the
applying of gas to said surface.
3. Apparatus as claimed in claim 2 including a mechanism for
applying a hydrating fluid to said treatment zone, said tip also
being slightly spaced from said surface during at least most of the
applying of said fluid to said surface.
4. Apparatus as claimed in claim 3 wherein said hydrating fluid and
said gas are water and air respectively.
5. Apparatus as claimed in claim 4 wherein the thickness of a water
layer formed by said hydrating fluid on said surface is limited to
prevent radiation energy loss.
6. Apparatus as claimed in claim 3 wherein said radiation is
applied as a sequence of pulses at a selected repetition rate; and
wherein said mechanism for applying a gas is operated during
intervals between at least selected ones of said pulses.
7. Apparatus as claimed in claim 6 wherein said mechanism for
applying a hydrating fluid is also operated at least in part
between at least selected ones of said pulses.
8. Apparatus as claimed in claim 7 wherein said mechanism for
applying hydrating fluid is operated followed by said mechanism for
applying gas between the same at least selected ones of said
pulses.
9. Apparatus as claimed in claim 7 wherein said mechanism for
applying hydrating fluid and said mechanism for applying a gas are
operated during different intervals between pulses.
10. Apparatus as claimed in claim 7 wherein operation of said
mechanism for applying a hydrating fluid overlaps at least selected
ones of said pulses.
11. Apparatus as claimed in claim 3 wherein said tip is in contact
with said surface during application of optical radiation to the
surface; and including a mechanism for selectively raising the tip
a slight distance from the surface during the application of
hydrating fluid and of gas thereto.
12. Apparatus as claimed in claim 11 wherein said mechanism for
selectively raising is driven at least one of hydraulically,
pneumatically, mechanically, electrically, magnetically and by
using energy of ablation.
13. Apparatus as claimed in claim 12 wherein said mechanism for
applying hydrating fluid applies the fluid under pressure, the
fluid pressure being used to raise the tip during operation of the
mechanism.
14. Apparatus as claimed in claim 12 wherein said mechanism for
applying a gas applies the gas under pressure, the gas pressure
being used to raise the tip during operation of the mechanism.
15. Apparatus as claimed in claim 13 including a mechanism for
scanning said tip in a direction substantially parallel to said
surface.
16. Apparatus as claimed in claim 2 including a mechanism for
facilitating scanning of said tip in a direction substantially
parallel to said surface, said mechanism including a feedback
mechanism to facilitate control of said scan for enhanced
cleaning.
17. Apparatus as claimed in claim 1 wherein said source is a laser
diode pumped solid state laser.
18. Apparatus as claimed in claim 17 wherein said source is wholly
located within said apparatus.
19. Apparatus as claimed in claim 17 wherein said solid state laser
is located in said apparatus and is connected to a diode laser
pumping array by at least one optical fiber.
20. Apparatus as claimed in claim 19 wherein each said diode is
connected to said solid state laser in a side pumping geometry.
21. Apparatus as claimed in claim 17 wherein said source a has a
geometry of a monolithic or flexible fiber laser
22. Apparatus as claimed in claim 17 wherein the radiation source
is one of a diode laser and a pumped laser cooled by phase change
material.
23. Apparatus as claimed in claim 22 wherein the residual of the
phase change material is used for cooling the treatment zone.
24. Apparatus as claimed in claim 17 wherein said solid state laser
and said pumping diodes are mounted as an array in heat sinking
electrodes which are cooled, the array being mounted in said
apparatus.
25. Apparatus as claimed in claim 1 including a reflector to return
particles of ablation and other energy from ablation to said
surface.
26. Apparatus as claimed in claim wherein said tissue is hard
biological tissue.
27. Apparatus as claimed in claim 26 wherein said tissue is one of
hard dental tissue and bone.
28. Apparatus for processing a hard material with optical radiation
from a suitable source including: a tip through which the radiation
is applied to a surface in a treatment zone of the material; and a
mechanism for applying a gas to said treatment zone to clean said
surface, said tip being slightly spaced from said surface during at
least a portion of the time gas is being applied.
29. Apparatus for processing a hard material with optical radiation
from a suitable source including: a tip through which the radiation
is applied to a surface in a treatment zone of the material; and a
mechanism for applying a hydrating fluid to said treatment zone,
said tip being slightly spaced from said surface during at least a
portion of the time said fluid is being applied.
30. A method for processing a hard material with optical radiation
from a suitable source including: applying radiation through a tip
to a surface in a treatment zone of the material; and cleaning the
treatment zone from dirt, including residual product of
ablation.
31. A method as claimed in claim 30 including the step of applying
a gas to said surface to clean the surface, said tip also being
slightly spaced from said surface during at least most of the
applying of gas to said surface.
32. A method as claimed in claim 31 including applying a hydrating
fluid to said treatment zone, said tip also being slightly spaced
from said surface during at least most of the applying of said
fluid to said surface.
33. A method as claimed in claim 32 wherein said hydrating fluid
and said gas are water and air respectively.
34. A method as claimed in claim 32 wherein said radiation is
applied as a sequence of pulses at a selected repetition rate; and
wherein said step of applying a gas is performed during intervals
between at least selected ones of said pulses.
35. A method as claimed in claim 34 wherein said step of applying a
hydrating fluid is also performed at least in part between at least
selected ones of said pulses.
36. A method as claimed in claim 35 wherein said step of applying
hydrating fluid is performed followed by said step of applying gas
between the same at least selected ones of said pulses.
37. A method as claimed in claim 35 wherein said step of applying
hydrating fluid and said step of applying a gas are performed
during different intervals between pulses.
38. A method as claimed in claim 35 wherein performance of said
step of applying a hydrating fluid overlaps at least selected ones
of said pulses.
39. A method as claimed in claim 32 wherein said tip is in contact
with said surface during application of optical radiation to the
surface; and including the step of selectively raising the tip a
slight distance from the surface during the application of
hydrating fluid and of gas thereto.
40. A method as claimed in claim 30 including scanning the tip in a
direction substantially parallel to said surface.
41. A method as claimed in claim 30 including returning particles
of ablation and other energy from ablation to said surface.
42. A method as claimed in claim 30 wherein said tissue is hard
biological tissue.
43. A method for processing a hard material with optical radiation
from a suitable source including: applying radiation through a tip
to a surface in a treatment zone of the material; and applying a
gas to said treatment zone to clean said surface, said tip being
slightly spaced from said surface during at least a portion of the
time gas is being applied.
Description
RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Application Serial No. 60/371,097, filed
on Apr. 9, 2002, which is herein incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] This invention relates to the processing of hard material,
and more particularly to the processing of such material with
optical radiation.
BACKGROUND OF THE INVENTION
[0003] Hard material such as a metal, dental material, such as
filling material or dental prosthesis material, or a hard
bio-tissue, for example tooth enamel dentine or bone, has
heretofore been ablated or otherwise processed by directing optical
radiation, and in particular, laser radiation, at the material.
However, the inventors have found that such procedures have in the
past been less optimally efficient for a number of reasons.
[0004] In particular, where a laser, for example an Er laser, is
being used to ablate bio-tissue such as tooth enamel, the
efficiency of the ablation can be significantly enhanced by
assuring adequate water content on the surface of the material
being treated and by keeping the irradiated surface of the material
free of dirt. The first condition is important because water
collected in natural cavities and in micro-cracks produced in the
material due to laser treatment may expand as a result of
irradiation, thereby assisting in the ablation process, and can
also generate shock waves which also facilitate the process. The
second condition is important to prevent dirt, including particles
of ablation, from interfering with light flow to the tissue
surface, such interference resulting both from such dirt blocking
radiation from reaching target material and from absorption of
radiation by such dirt. It has been found by the inventors that the
second condition alone can increase ablation efficiency by roughly
30% to 500%. The two conditions together can result in a many-fold
increase in efficiency.
[0005] However, hydrating and cleaning the tissue or other hard
material during treatment is normally difficult where the light
guide through which the radiation is applied to the material is in
contact with the material, as is preferably the case, the light
guide preventing water from reaching the tissue under the light
guide for hydration, and preventing ablation products from leaving
the area under the light guide. Except for embodiments such as that
shown in copending application Ser. No. 09/549,406, or other
embodiments where ablation products and other energy resulting from
the ablation process are recycled, contact between the light guide
and/or any particular other energy reflector rounding the light
guide and the tissue during irradiation is usually desirable in
that it results in less photon loss, and thus higher ablation
efficiency. By hydrating, cleaning and recycling energy lost from
the ablation process, optimum enhancement of ablation efficiency
can be achieved, permitting smaller and less expensive radiation
sources to be used for the material processing.
[0006] A need therefore exists for a method and apparatus which
facilitates hydration and cleaning of hard material, and in
particular hard tissue such as tooth enamel, during
ablation/processing of the material, and which preferably also
facilitates recycling of ablation products/lost energy, so as to
optimize ablation/processing efficiency. Improved and novel laser
sources which take advantage of the lower energy requirements
resulting from the enhanced ablation efficiency to provide required
energy with smaller and less expensive units are also
desirable.
SUMMARY OF THE INVENTION
[0007] In accordance with the above, this invention provides a
method and apparatus for processing a hard material with optical
radiation from a suitable source. The radiation is applied through
a tip to a surface in a treatment zone of the material, and the
treatment zone is cleaned by a suitable mechanism of dirt,
including products of ablation. The tip is slightly spaced from the
material surface during at least most of the time a gas, such as
air, is applied by a suitable mechanism to the surface for the
cleaning thereof. A hydrating fluid such as water may also be
applied by a suitable mechanism to the treatment zone, the tip
through which radiation is applied being slightly spaced from the
surface of the material during at least a portion of the time the
hydrating fluid is being applied. The thickness of a water layer
formed by the hydrating fluid on the treatment surface is limited
to prevent radiation energy loss. The radiation may be applied as a
sequence of pulses at a selected repetition rate, with the gas
being applied during intervals between at least selected ones of
the radiation pulses. The hydrating fluid may also be applied at
least in part between at least selected ones of the radiation
pulses. The applying of the hydrating fluid may be followed by the
applying of the gas between the same radiation pulses, the
hydrating fluid and the gas may be applied during different
intervals between pulses or the applying of hydrating fluid may
overlap with at least selected ones of the radiation pulses.
[0008] For some embodiments, the tip is in contact with the surface
of the material during irradiation of the surface and the tip is
selectively raised a slight distance from the surface by a suitable
mechanism during the application of at least one of the hydrating
fluid and the gas, and preferably both. The mechanism for
selectively raising the tip may be driven hydraulically,
pneumatically, mechanically, electrically, magnetically or by using
energy of ablation. The hydrating fluid and/or the gas may be
applied under pressure, with the fluid/gas pressure being used to
raise the tip. The tip may also be scanned by a suitable mechanism
in a direction substantially parallel to the treatment surface,
which mechanism may include a feedback mechanism to facilitate
control of the scan for enhanced cleaning.
[0009] The radiation source may be a laser diode pumped solid state
laser. The radiation source may be wholly located within the
apparatus or the solid state laser may be located in the apparatus
and be connected to a diode pumping array by at least one optical
fiber. In the later case, each diode of the array may be connected
to the solid state laser in a side pumping geometry. The source may
also have the geometry of a monolithic or flexible fiber laser, or
may be a diode laser or a pumped laser cooled by phase change
material. The residual of any phase change material used to cool
the source may be used to cool the treatment zone. The solid state
laser and the pumping diodes may also be mounted as an array in
heat sinking electrodes which are cooled by a pressurized gas, the
array being mounted in the apparatus.
[0010] Particles of ablation and other energy from the ablation may
be returned to the treatment surface to enhance the efficiency of
the ablation by a reflector or other suitable mechanism.
[0011] The hard material being processed may be hard biological
tissue, for example bone or hard dental tissue such as enamel, or
may be dental material such as filling material or material used
for various dental prosthesis.
[0012] The forgoing objects features and advantages of the
invention will be apparent from the following more detailed
description of the invention as illustrated in the accompanying
drawings, common elements in the various figures having the same or
comparable reference numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a partially cut-away illustration of one
embodiment of apparatus in accordance with the invention.
[0014] FIG. 2 is a diagram of an illustrative process sequence for
practicing the invention.
[0015] FIG. 3 is a partially cut-away illustration of a second
embodiment of apparatus in accordance with the invention.
[0016] FIG. 3A is a sectional view taken along the line A-A in FIG.
3.
[0017] FIG. 4 is a partially cut-away illustration of a third
embodiment of apparatus in accordance with the invention.
[0018] FIG. 5 is a partially cut-away illustration of a fourth
embodiment of apparatus in accordance with the invention.
[0019] FIG. 6 is a partially cut-away illustration of a fifth
embodiment of apparatus in accordance with the invention.
[0020] FIG. 6A is a sectional view taken along the line A-A in FIG.
6.
[0021] FIG. 7 is a schematic representation of a laser diode pumped
solid state laser suitable for practicing the teachings of this
invention.
[0022] FIG. 7A is a sectional view taken along the line A-A in FIG.
7.
[0023] FIG. 8 is a schematic representation illustrating the novel
concepts of this invention.
DETAILED DESCRIPTION
[0024] In general, the invention involves selectively providing
hydration, cleaning and/or recycling of energy resulting from
ablation to enhance ablation efficiency and providing a small gap
between the tip of an optical light guide used to direct radiation
to the material surface, at least during periods when hydration of
the surface being treated is occurring and during cleaning of the
surface. For some embodiments, the gap may also be provided during
irradiation to facilitate the recycling of ablation products/energy
to the material. For other embodiments, the tip is in contact with
the treated surface during irradiation and recycling may be
primarily of energy. The improved efficiency of the ablation
permits the process to be performed using smaller and less
expensive laser radiation sources, and in particular diode laser or
diode/fiber laser pumped radiation sources which may be small
enough to fit in a treatment hand-piece.
[0025] FIG. 8 illustrates the general concept of the novel method
and apparatus of this invention. Light pulse 55 passes through
optical tip 5 and is delivered to processed zone 56 of the tissue
or material 58. Gas 57 and liquid 58 flow through controlling valve
59, channel 60 and gap 61 between tip 5 and surrounding tube 8 to
the same zone 56. The gas pulses are selectively synchronized with
the light pulse. Pressure pulses formed as a result of the gas
pulse increase the gap between of treated zone 60 and the end of
the tip between light pulses, thereby cleaning residual products of
ablation produced as a result of the light pulses. Water or other
liquid pulses may be delivered to the treatment zone between gas
pulses for hydration, cooling and/or initiation of the ablation
process. The tip is thus oscillating in direction 62 as a result of
the above actions.
[0026] FIG. 1 is a semi-schematic, partially cut-away view of a
first embodiment for practicing the teachings of the invention. For
this embodiment, laser radiation from a source (not shown), for
example a laser rod, is applied through an optical fiber or other
suitable optical component 1 fixed in a handle or other housing 2
to an optical reflector 3 mounted in a housing 4. Optical radiation
reflected from reflector 3 is directed through an optical guide or
tip to the object being treated, for example hard tooth tissue.
Optical tip 5 is fixed at its light-receiving end in a holder 7 and
extends through an optically opaque tube 8 mounted in a housing 10
and in a cover 9 for the housing. Tube 8 may be of any suitable
material, but, if not a disposable component, is preferably of a
material harder then the material being treated, for example
stainless steel, ceramic or tungsten. Housing 10 is attached to
handle 2. A fixed sleeve or tube 11 is mounted inside housing 10
and a movable/traveling sleeve or tube 12 is mounted inside tube 11
holder 7 is hermetically attached to movable tube 12, for example
by threading. Tubes 11 and 12 have adjacent indentations in which
sealing rings 13 are mounted. Cover 9, housing 10, and tubes 11, 12
have aligned openings formed therein through which radiation from
fiber 1 passes.
[0027] Pressurized water is applied from tank 19 through tube 14,
coupling 15, and channel 16 to space 17. Tube 14 extends into the
water in tank 19. Pressurized air is applied from tank 20 through
connecting tube 33, coupling 32 and a channel (not shown) which
extends to space 17 between housing 10 and tube 11 at a location
radially spaced from channel 16. Compressor 18 pressurizes both
tanks 19 and 20 through tube 23 and valve 21/tube 26 and valve
22/tube 27 respectively. Compressor 18 is also connected to
atmosphere through tubes 23, 24 and valve 25. Valve 25 is normally
closed. Tank 19 is incompletely filled with water and can connect
to atmosphere through tube 28 and normally closed valve 29. Tank 20
connects to atmosphere through tube 30 and normally closed valve
31.
[0028] To provide water to space 17, compressor 18 is turned on,
valve 22 is closed, valve 21 is opened, and valves 25 and 29 are
closed. Water flows from space 17 to the space between optical tip
5 and tube 8 and through this space to wet the surface of object 6.
Excess or residual water leaves the treatment zone defined by tube
8 through slits 34 formed in the tube. Since the gap between
optical tip 5 and tube 8 is substantially smaller then the depth of
space 17, there is a pressure build-up in space 17 which acts on
holder 7 and traveling sleeve 12 attached thereto to raise the
holder and sleeve, and thus raises light guide or tip 5 fixed in
holder 7 from the surface of object 6. The tip remains raised,
permitting water to hydrate and cool the zone of object 6 under the
tip, until valve 21 is closed to terminate water flow. Similarly,
pressurized air is applied to space 17 by turning on compressor 18,
opening valve 22 and closing valves 21, 25, and 31. Pressurized air
in space 17 also raises the tip in the same manner as the
pressurized water, and also flows through the space between tip 5
and tube 8 to clean the surface of object 6, excess air, along with
excess water and products of ablation and other dirt in the
treatment zone flowing out of the zone through slits 34 in tube 8.
Air pressurization of space 17 is ended by closing valve 22 and
opening valves 25, 29, and 31, permitting the pressure in space 17
to be equalized to atmospheric pressure. This permits holder 7 and
traveling tube 12, and thus tip 5 affixed thereto, to be moved
downward by spring 35 until the tip is again in contact with the
object 6. The distance that tip 5 is raised can vary with
application, being approximately 100 to 150 .mu.m for illustrative
embodiments.
[0029] All of the valves are electrically controlled by a suitable
processor or other control mechanism to operate the laser
radiation, water and air delivery in a desired sequence. One
possible sequence is to operate the laser at a desired pulse
repetition rate, for example 5-100 Hz., more preferable 10-30 Hz
with water and air being applied in the intervals between each
laser pulse, or between selected laser pulses, for example in the
interval between every third pulse. Another option is for the
application of water and the application of air to be between
different ones of the laser pulses. Thus, water could be applied
between every other laser pulse, with air being applied between the
laser pulses where water is not applied. FIG. 2 illustrates still
another option where the application of water W overlaps selected
laser pulses L, with air A being applied in the interval between
laser pulses after the interval during which the water is applied.
In this case, the water pressure builds up slowly enough so that
the tip does not rise off the surface of object 6 against the force
of spring 35 until the overlapped laser pulse is over. The
advantage of this embodiment is that water can also cool the object
during and immediately after irradiation. Modeling data indicates
that, where an Er laser is used, the thickness of the water film in
the processing zone before irradiation by a laser pulse should be
in the range 5-200 microns, and preferable 5-50 microns.
[0030] While for the embodiment of FIG. 1, tip 5 is raised by water
pressure (hydraulic action) and air pressure (pneumatic action),
this is not a limitation on the invention, and other suitable
mechanisms may be utilized for the raising and lowering of the tip.
For example, FIG. 3 shows a drive mechanism 37 positioned adjacent
spring 35 which can be processor controlled to raise tip 5 as
desired, the tip being lowered when mechanism 37 is deactivated
under action of spring 35. Alternatively, mechanism 37 might be
utilized to both raise and lower tip 5, with spring 35 no longer
being required. Mechanism 37 may be a solenoid drive,
electromagnetic drive, piezoelectric drive, other motor drive etc.
and may for example transform electrical energy, magnetic field
energy, mechanical energy or thermal energy into movement of the
tip. The raising of tip 5 can also be effected by a blast effect
from laser ablation on for example water on and in the object, a
shock wave from the blast acting on the tip to raise it. On
termination of the blast effect, spring 35 returns the tip to its
lowered position in contact with object 6.
[0031] FIG. 3 also shows a reflector 36 mounted at the end of tube
8, the reflector being operative to increase the efficiency of the
treatment device. The diameter of reflector 36 can be 0.1 mm to 4
mm in excess of the diameter of optical tip 5 for preferred
embodiments. Reflector 36 functions differently depending on
whether tip 5 is or is not in contact with object 6 during laser
irradiation. If tip 5 is spaced from the surface of object 6 by
some interval during irradiation, reflector 36 returns to the
treatment zone products of laser ablation as fragments of solid
particles. These particles further facilitate the ablation process
in the manner generally described in the copending application, the
subject matter of which application is incorporated herein in its
entirety by reference. If optical tip 5 is in contact with the
surface of object 6 during irradiation, ablation particles are
directed to the area directly surrounding the treatment zone,
generally facilitating the ablation process. In either event, shock
waves resulting from the laser ablation are returned to the area of
treatment and act on the object, for example dental enamel, to
facilitate the ablation thereof. Slots 34 in reflector 36 perform
the same functions as the slots 34 in tube 8, permitting the
release of excess water and air, as well as products of ablation
and other dirt to be removed from the treatment zone. Pressure or
shock waves from ablation can also be used for raising the tip
between pulses to facilitate cleaning products of ablation from the
treatment zone. Spring 35, gas pressure, water pressure or other
suitable mechanisms can be used to subsequently return the tip to
contact with treatment zone 56.
[0032] Another embodiment of the invention includes a mechanism for
moving or scanning the tip across or parallel to the treatment
zone. The scanning mode can be 1D or 2D. This scanning can be
combined with raising the tip perpendicular to treatment zone (3D
scanning). Scanning of the tip can be done manually by a dentist or
other operator. A feed back mechanism can be used to assist the
manual scanning by showing when proper cleaning of products of
ablation and any other dirt has occurred and/or where such cleaning
is required. For example, an acoustic or optical signal may depend
from detected ablation efficiency and/or material of ablation. If
manual scanning it is not being performed properly to achieve
desired results, the device, by sound or lighting, can inform the
operator of the problem so that he can correct it. Automatic
scanning control may also be possible in response to feedback
signals.
[0033] Since the enhanced ablation efficiency resulting from
practicing the teachings of the invention can result in a two to
three fold and more improvement in ablation for a given laser
pulse, practicing the teachings of the invention significantly
lowers the energy requirements for the laser source used, and in
particular, should permit the use of diode laser pumped solid state
lasers as the radiation source. In the past, the energy needed for
treatment has required too many diode lasers for such sources to be
economically feasible. This may also permit the source to be small
enough to fit in the treatment hand-piece, for example in the
handle 2 thereof. The radiation source can, for example, be an
Er:YAG crystal pumped by diode lasers with a wavelength of 960-980
nm. Other suitable active elements include, but are not limited to,
Cr:ILF, Er:YSGG and other crystal doped with Cr, Tin and Ho with
emitting wavelength 2.6-3.2 micron and an output energy of 1-1000
mJ with a repetition rate of 1-1000 Hz and a pulse width of
10(-9)-10(-2). The advantages of solid state lasers with diode
pumping is that they are more efficient in converting electrical
energy to optical energy and generally have a smaller size. Where
less diodes are required, such source can also be less
expensive.
[0034] Diode laser(s) may also be used alone as the radiation
source. For example, a diode laser based on AlInGaAsSb/GaSb with
separate confinement-heterostructure quantum well can be used to
generate wavelengths in the band of peak absorption of water and
hydroxiapatite, 2.6-3 microns. The diode laser(s) can be mounted in
the handpiece and cooled by water, vaporized liquid or melted solid
state (i.e., ice).
[0035] In FIG. 3, the laser source is in the handle of the
hand-piece. This arrangement is more reliable in that it eliminates
the need for using accident-prone IR optical wave guides in an
umbilical connecting the source to the hand-piece. However, this
embodiment does require high energy electrical power cords in the
umbilical which can be stiff, making the hand-piece more cumbersome
to use. Referring to FIG. 3A, pumping of active rod 38 (for
example, Er:YAG crystal) is accomplished by from two to ten diode
bars 39. Active rod 38 and diode bars 39 are cooled by water from
water tank 19, tube 14 leading through heat exchanger 40 for the
laser source to tube 41 which connects to fitting 15 of housing 10.
Diode bars 39 are connected to power supply 42 by electrical wires
43. The end surfaces of active rod 38 have dielectric coatings
which function as mirrors for the laser cavity, the cavity lasing
in standard fashion.
[0036] FIG. 4 shows the pumping of active rod 38 being done by
diodes located outside the hand-piece. For this embodiment,
radiation from a plurality of diode bars 39 pass through a suitable
optical system 44 to enter an optical monofiber 45 connected to
deliver the radiation to one end of the active rod. As shown in
FIG. 5, pumping of active rod 38 can also be performed with optics
which connect the outputs from the diodes 39 through suitable
optical elements 44 and a plurality of optical fibers 45 to the
walls of the active rod, the contact of the fibers with the walls
permitting energy to enter the cavity for pumping. Element 46 is an
optical connector.
[0037] The pumping of active rod 38 can also be performed by use of
several optical monofibers 45 connected to the active rod in a so
called side pumping geometry as shown in FIG. 6. For this
embodiment, radiation from each diode bar passes through a optical
system 47 to the input of a monofiber 45. For the side pumping
geometry, the fibers with removed cladding are in contact with the
walls of the active rod along an extended length of the fiber and
radiation from the fiber is coupled to the rod along this entire
contact length. The refractive index of the crystal/rod is higher
then the refractive index of the fiber 45.
[0038] In other embodiment active rod or slab 38 is mounted in
non-doped cylinder 40 or between to non-doped plates with
refractive index lower than the active rod and optically connected
with the active rod or slab from a side surface thereof. This
assembly has fiber laser geometry. Energy from the diode is coupled
into a non-doped zone and from the non-doped zone, coupled into the
active zone. This assembly can be made as a flexible fiber with
doped core and non-doped cladding.
[0039] FIG. 7 shows a small, pumped solid-state laser which can be
packaged into the hand-piece. Active element 38' (on FIG. 7 it is
46) is a slab or rod crystal doped by ions (for example Er). Active
element 38' is pumped by diode bars 39' (not shown) mounted between
electrodes/heat sinks 48. Electrodes/heat sinks 48 are thermally
and electrically attached to bars 39' and thermally attached to
active element 38'. The high reflective coating for diode bar
wavelength 49 helps to couple diode energy into the active element.
A high pressure compressed gas, for example R134A, from a can 51 is
used for cooling active element 38', diodes 39' and electrodes/heat
sinks 48. The low temperature liquid gas from can 51 is released
into holes 50, a valve 53 being used to control the temperature of
the cooled components to within a desired range. Tubes 52 and 54
are used for delivery of the gas to the laser assembly high
pressure gas or super cooled liquid, for example freon, nitrogen,
or CO2, can be used for cooling diode lasers and/or pumped solid
state laser and/or or treatment tissue in all the various
embodiments. Low pressure water with an evaporation temperature of
20-50C can also be used for same propose. In this case, the cooled
side of the laser should be connected with a vacuum pump. In other
embodiments, a melted or other phase change compound such as ice
can be used to cool the diode laser and pumped solid state laser.
Residual melted water can be used for cooling treated
material/tissue.
[0040] A prototype of the invention described above was constructed
and tested on laser removal/ablation of tooth enamel. During the
experiments, a standard device of the general type shown in U.S.
Pat. No. 5,257,956 was used with tip contact during irradiation and
a sequence of irradiation, water application and pressurized air
application generally as shown in FIG. 2. Human fresh extracted
teeth were used. The laser source used was a pulsed Er:YAG laser
operating at 2.94 .mu.m and having a pulse width (FWHM) of
(200.+-.20) .mu.s. Radiation energy at the optical tip output was
about 210 mJ and the laser pulse repetition rate was 10 Hz. The
diameter of the optical tip was 550 .mu.m. The consumption of
cooling water was (0.25.+-.0.02) ml/min. The pressure formed by the
compressor 18 was about 3 bar, this resulting in the raising of the
tip from the enamel surface by approximately (120.+-.15) .mu.m.
Enamel plates having a thickness of 1 mm were irradiated by a
series of laser pulses having an energy density of (70.+-.10)
J/cm.sup.2, irradiation stopping when through ablation of the plate
occurred. Enamel removal velocity was calculated as a ratio of
plate thickness to the number of laser pulses used to achieve
through ablation. It was found that, while enamel removal velocity
for a standard device was (21.+-.3) .mu.m/pulse, enamel laser
removal velocity utilizing the teachings of this invention was
(55.+-.5) .mu.m/pulse. Thus, the device utilizing the teachings of
this invention was about 2.5 faster in treatment then the standard
one.
[0041] While for the illustrative embodiments shown, only tip 5 is
raised to facilitate hydration and cleaning of the object surface
under the tip, this is not a limitation on the invention, and the
objective of raising the tip could also be accomplished by having
tube 8 and tip 5 raised together, by raising housing 10 or in other
suitable ways. Similarly, while a mechanical spring 35 has been
show as the return mechanism for the illustrative embodiments,
other suitable elastic components might be utilized to perform this
function, for example an air spring or an elastomer. Further, while
the invention has been used to treat tooth enamel for preferred
embodiments, the invention could also be used to treat other hard
materials such as bone tissue, metals, diamond, sapphire, etc.
Other variations in the details of construction are also within the
contemplation of the invention. Thus, while the invention has been
particularly shown and described above with reference to preferred
embodiments, the forgoing and other changes in form and detail may
be made therein by one skilled in the art while still remaining
within the spirit and scope of the invention, which is to be
defined only by the following claims.
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